494
AWUS01 KWNH 291858
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-300057-

Mesoscale Precipitation Discussion 0512
NWS Weather Prediction Center College Park MD
258 PM EDT Sat Jun 29 2024

Areas affected...Southern and Eastern OH...Northern WV...Western
MD...Western and Central PA

Concerning...Heavy rainfall...Flash flooding likely

Valid 291857Z - 300057Z

SUMMARY...Broken bands of showers and thunderstorms with very
heavy rainfall rates will likely result in scattered instances of
flash flooding later this afternoon and into the evening hours.

DISCUSSION...An anomalously moist and moderately unstable airmass
is pooled up across the Upper OH Valley and the northern
Mid-Atlantic region as deeper layer southwest flow continues well
ahead of an upper-level trough and associated cold front over the
Upper Midwest and Upper Great Lakes region. MLCAPE values across
areas of southern and eastern OH, northern WV and far western PA
have increased to 1500 to 2500 J/kg, and the latest RAP analysis
shows effective bulk shear values of about 30 to 40 kts.

GOES-E Airmass RGB satellite imagery suggests some weak vort
energy aloft also transiting the OH Valley as a belt of stronger
mid-level winds arrives ahead of the aforementioned upper-level
trough. This energy coupled with the favorable thermodynamic and
kinematic environment will favor broken bands of convection over
the next several hours spanning the remainder of the afternoon and
the evening time frame. The areas that should see the greatest
impacts will be across much of southern and eastern OH, northern
WV, western MD, and much of central and western PA.

The latest NESDIS Blended TPW product shows very high PWs over the
OH Valley that are stretching well across northern WV and western
PA. PWs of 2.0 to 2.25 inches are noted across the region, and the
CIRA-ALPW data confirms a highly anomalous and deep level of
tropical moisture in place. This will set the stage for convection
to be produce very high rainfall rates this afternoon and evening
as storms organize and grow in intensity.

Rainfall rates of 2.0 to 2.5 inches/hour are expected with the
stronger storms, and the latest hires model CAMs suggest
eventually some localized concerns for cell-training and possible
cell-merger activity. As a result, going through early this
evening, some rainfall totals may locally reach 3 to 4+ inches.

Given the rainfall potential and added consideration of some of
these heavier rates and totals impacting multiple urban
environments, scattered instances of flash flooding are likely to
occur.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...BGM...CTP...ILN...LWX...PBZ...PHI...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON   41647714 41467599 40397620 39207937 38598290
            38918441 39428444 39668383 40518122 41267861